1. Field of the Invention
The present invention relates to a freezing tank for making ice cream, more particularly to a freezing tank which permits convenient and precise detection of a leakage so as to ensure a leak-proofing effect thereof.
2. Description of the Related Art
Referring to FIG. 1, a conventional freezing tank 10 for making ice cream is shown to include an outer tank 11 which has a first open end 111, and an inner tank 13 which is placed in the outer tank 11 to confine a cooling chamber 14 with the outer tank 11 for receiving a freezing fluid 12 and which has a second open end 131 jointed to the first open end 111 in a fluid-tight relationship to prevent leakage of the freezing fluid 12.
After a sealing process for sealing the first open end 111 of the outer tank 11 to the second open end 131 of the inner tank 13, the resulting freezing tank 10 must be subjected to a quality control process for detection of a leakage of the freezing fluid 12. Conventionally, the detection is conducted by placing the freezing tank 10 in water and inspecting if bubbles are generated at the juncture of the first and second open ends 111, 131. Generation of bubbles indicates the presence of a leakage at the juncture. However, since the cooling chamber 14 is filled with the freezing fluid 12, and since there is no significant pressure difference between an interior and an exterior of the cooling chamber 14, bubbles are not easily detected when the leakage is relatively small. Thus, the operator may not be able to successfully detect the presence of a defective freezing tank 10. Leakage or vaporization of the freezing fluid 12 from the cooling chamber 14 of the defective freezing tank 10 can result in a reduced freezing effect and in harm to the user's health.